Condensed Statements of Operations and Comprehensive Loss (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Research and development expense to related party	$ 143	$ 1,011	$ 458	$ 1,123

Research and development expense to related party.

No definition available.

Name:	pcvx_ResearchAndDevelopmentExpenseToRelatedParty
Namespace Prefix:	pcvx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration